Versions
This page outlines the changes and known limitations associated with different versions of EASE-Grid. The original version of EASE-Grid was released in 1992 and the latest version, EASE-Grid 2.0, was defined in 2011. Table 1 summarizes the differences between the two versions.
| Feature | Original EASE-Grid | EASE-Grid 2.0 |
|---|---|---|
| Projection ellipsoid | International 1924 Authalic Sphere |
WGS 84 |
| Pole location | Center of cell | Intersection of center cells |
| Scale (data-set specific) | Azimuthal/Cylindrical coupled (such as Nl/Sl/Ml 25.067525 km) | Azimuthal: Exact (such as 25.0 km or 36.0 km) Cylindrical: Integer-multiples across latitude of true scale |
| Dimensions | Odd-numbered (721 x 721) | Even-numbered (720 x 720) |
| Nested Grids | Must choose between total coverage and nested cells | Coverage can stay the same, only number of cells changes |
| Corner Points | Corner cell locations in azimuthal grids are undefined | No undefined corner cells |
| GeoTIFF | Requires reprojection | Supported without reprojection1 |
| Software Issues | Usually requires user to understand custom projection settings | Most software supported1 |
| 1 Achieved by setting projection ellipsoid to reference datum |
||
Software Support
Table 2 summarizes the current state of support for EASE-Grid format data when used with current popular software packages. Table 2 also lists geodetic parameter data set codes from the European Petroleum Survey Group (EPSG) for both the original EASE-Grid and 2.0 versions. EPSG codes are helpful shortcuts for PROJ.4 software, and for software that depends on PROJ.4, such as GDAL Tools.
| Software & Codes |
Original EASE-Grid (Spherical Projection) |
EASE-Grid 2.0 (WGS 84 Projection) |
Current Status |
|---|---|---|---|
| HDFEOS 2.xx HDFEOS 5.xx |
Supported | Cylindrical projection is supported.
Azimuthal is not supported. |
HDF depends on GCTP. NSIDC may propose a change to GCTP to support Lambert Azimuthal with ellipsoid. |
| PROJ.4 | Supported | Azimuthal and cylindrical EASE-Grid 2.0 supported in PROJ 4.8.0 (13 March 2012). Azimuthal projection was supported in PROJ 4.7.0 (23 September 2009). Bug in PROJ 4.7.0 resulted in error of ~15 km when transforming points near equator for cylindrical EASE-Grid 2.0 data. | Both original EASE-Grid and EASE-Grid 2.0 are fully supported as of PROJ 4.8.0 (13 March 2012). |
| GDAL Tools | Supported | Supported, with correct version of PROJ.4. | User must ensure correct PROJ.4 is installed; see PROJ.4 notes. |
| EPSG Codes | North: 3408 South: 3409 Global: 3410 |
North: 3973 South: 3974 Global: 3975 |
PROJ 4.8.0 is required to obtain correct values for EASE-Grid 2.0 cylindrical. |
| ENVI | Azimuthal supported. T. Haran (NSIDC) has written procedure to add cylindrical equal-area to ENVI. Requires simple modifications to support header information for EASE-Grid data sets. ENVI cannot read/write user-defined projection information from/to GeoTIFF, but it can do so with its own ENVI header format. |
Azimuthal supported. Cylindrical equal-area requires user-defined projection information; simple modifications to support header information for EASE-Grid 2.0 data sets are forthcoming. |
Simple modifications are required for cylindrical equal-area in both EASE-Grid versions; see respective column for current status. |
| Mapx | Supported | Supported | N/A |
| ArcGIS | Supported | Supported | N/A |
| ERDAS | Supported | Supported | N/A |
Page last updated: 2/11/14
